There has been increasing evidence that the alteration of antioxidant enzymes such as manganese superoxide dismutase (MnSOD) might be implicated in the development of schizophrenia and/or tardive dyskinesia (TD). This study investigated the association of a MnSOD gene (MnSOD) polymorphism (Ala-9Val) with schizophrenia as well as its involvement in TD. Patients with schizophrenia (n=262) and healthy controls (n=263) were enrolled in this study and genotyped by a polymerase chain reaction-based method. The distribution of the MnSOD genotypes and alleles was not significantly different between patients and controls. Logistic regression analysis also failed to reveal any association between MnSOD genotypes and TD. Taken together, these results suggest that the MnSOD polymorphism does not contribute to the development of schizophrenia and/or TD, at least in the Korean population.